The chemical structures of bile pigments found in the gallbladder and meconium as well as in other body fluids of newborn human infants, mature and premature, will be studied at autopsy. Similar studies will be performed in newborn monkeys. These pigments will be studied by spectroscopic and chromatographic methods, as well as by mass spectroscopy and nucleic magnetic resonance. We plan to study the origin of these compounds and their metabolism and excretion in experimental animals by studies with radioactive isotopes.